Congrats!

Glad to hear that you got it worked out. I have run into the same issue w/ Model1 Sales. In one case, I had to throat and finish ream the chamber in order to get a round to seat fully. For future reference, the green scotch pad method is the least invasive way to clean up a chamber. I takes very little away in terms of actual metal. If you followed the tecchnique you described, you should be fine! I use an in and out technique to create a swirl pattern inside the chamber, kind of like polishing brake slave cylinders or V8 cylinders.

One thing to always remember: Never mess with the gas port size! A burr in the bore can ruin your whole day! Not to mention the really heavy recoil if you overbore it! Accuracy tends to suffer a lot under these circumstances.

I wasn't about to enlarge the gas port, the brl isn't that short. I'm glad you guys mentioned polishing the bore, the only thing I could think of was headspace. I knew the problem was in the chamber and not with the ejector or anything else. I just didn't know what was wrong with the chamber. I figured someone here would know! Thank you guys for the help!

I've had the same exact experience with a DPMS upper I bought several years ago. It wouldn't eject the empty casings all the time and the brass was showing signs of a gouged chamber. It would've been impossible to full length resize. Must've had a chip or burr when maching the chamber or possibly not enough coolant? I purchased the upper new/complete from a vendor at a local gunshow. He said he'd take it back to his shop and polish it up. The brass bulges were so deep, I told him I felt it was a manufacturing defect and wanted the barrel replaced. It was sent back to DPMS and was replaced with a new upper n/c.

Glad to hear you got it working. It can be pretty frustrating to have a gun that doesn't work correctly.

Yep, I was pissed this weekend when my AR stopped working! I am not sure what's wrong. It might be ammo. I was using Wolf, which I hear is crap. It also might be that I didn't run the rifle wet (or wet enough).

It would go bang and not extract the round, it would be jammed half extracted. I think it's the ammo because the week before it would cycle but jammed on feeding frangible ammo (wouldn't pick it up). Prior to that, I cycled 200 rounds with no failures to feed or extract. Ammo was different all three times, this is a DPMS CMP with the HBAR barrel.

Any ideas? I think it's picky about ammo. I couldn't find any problems while cleaning it.

I'm no expert, but my shootin' buddys rifle was doing the same thing and his gas block was mis-aligned with the barrel gas port. After we re-aligned the gas port it cycled flawlessly no matter what type ammo we shot.
Easy and cheap fix.

I'm no expert, but my shootin' buddys rifle was doing the same thing and his gas block was mis-aligned with the barrel gas port. After we re-aligned the gas port it cycled flawlessly no matter what type ammo we shot.
Easy and cheap fix.

It's worth looking at, but I suspect that's not it. We'll see. I do know that it's a problem with the upper, so it's worth a look see.